Systems for data stream encoding, transport, decoding, and related processing are well known in the art. One particular example of such a system is the well-known MPEG-2 system; salient aspects of the MPEG-2 system are described in the following documents:
International Standard ISO/IEC 13818-1: MPEG-2 Part 1 (Systems); and
International Standard ISO/IEC 13818-6: MPEG-2 Part 6 (DSM-CC), sections 8 and 9.
The term “encoded” is used throughout the present specification and claims, in all its grammatical forms, to refer to any type of data stream encoding including, for example and without limiting the scope of the definition, well known types of encoding such as MPEG-2 encoding. It is appreciated that an encoded data stream is generally more difficult to read, in the sense that more processing and typically more time are required to read an encoded data stream than a data stream which is not encoded.
The terms “scrambled” and “encrypted”, in all of their grammatical forms, are used interchangeably throughout the present specification and claims to refer to any appropriate scrambling and/or encryption methods for scrambling and/or encrypting a data stream, and/or any other appropriate method for making a data stream unintelligible except to an intended recipient thereof.
Systems for aiding in providing random access to content in a data stream, particularly in a stored data stream, are known in the art. As will be appreciated by persons skilled in the art, such systems are of particular use with encoded and/or encrypted data streams.
Published PCT Patent Application WO 99/62251 of Koninklijke Philips Electronics NV describes a system in which a data stream is stored and, at the time of storage, an index to the data stream is built.
Published PCT Patent Application WO 01/35669 of NDS Limited and corresponding national applications, including U.S. patent application Ser. No. 09/574,096 of Darshan et al, describes a method for processing a data stream in which an index of candidate access points to the data stream is built and stored, typically as the data stream is received and stored. As stated in WO 01/35669, for the case of the MPEG-2 system, the inventors “determined that the presentation time of a bit and the arrival time of a bit generally differ by no more than a short time such as, for example, approximately 0.5 seconds.” It will be appreciated by persons skilled in the art that the characteristic of MPEG-2 systems determined by the inventors of WO 01/35669 would be of use in finding a bit having a desired presentation time provided that the presentation time of a previous bit, such as the first bit in a stream comprising the bits, and relevant bit arrival times are known.
The disclosures of WO 01/35669 and corresponding U.S. patent application Ser. No. 09/574,096 of Darshan et al are hereby incorporated herein by reference.
An advanced television system including storage is described in published PCT patent application WO 00/01149 of NDS Limited and corresponding U.S. patent application Ser. No. 09/515,118 of Wachtfogel et al, the disclosures of which are hereby incorporated herein by reference.
The present application claims priority from UK Patent Application 0117926.6, filed 23 Jul. 2001, and U.S. Provisional Patent Application No. 60/308,076, filed 26 Jul. 2001, the disclosures of which are hereby incorporated herein by reference.
The disclosures of all references mentioned above and throughout the present specification are hereby incorporated herein by reference.